This invention relates to a tube support arrangement and, more particularly, to a clamped tube support construction for supporting horizontal tubes from vertical support tubes, at opposite sides thereof, particularly in a pressurized fluid bed boiler.
The in-bed heating surface of the evaporator or secondary superheater surfaces of certain pressurized fluid bed boiler designs includes horizontally positioned tubes. These horizontal tubes are typically supported by generally vertical support tubes that are slightly inclined from a truly vertical position.
In the past, pairs of lugs have been welded to opposite sides of the vertical support tube at longitudinally spaced intervals to form lower and upper lugs that have spaces therebetween through which the horizontal tubes extend. The horizontal tubes are closely-fitted between the lower and upper lugs and supported by the lower lug on each side of the vertical support tube. This construction permits the horizontal tubes to slide horizontally while assuring that the horizontal tubes remain in a vertically fixed position. However, if a horizontal tube needs to be repaired or replaced, the weld connection between the upper lug and the vertical support tube must be disadvantageously burned-off, thereby necessitating both replacement of the upper lug and rewelding of the new upper lug when the repairs are completed. The welding and rewelding is also detrimental to protective coatings that may be used on the tubes to increase bed surface life of the primary and evaporator tubes in the erosive environment of a fluidized bed. A need exists, therefore, for a simple, nonwelded horizontal tube support construction for pressurized fluid bed boilers that can survive an environment more severe than any in current, commercial power plant applications which at hottest points will approach surface design temperatures of 1600 to 1700 degrees Fahrenheit. This need, which is satisfied by the embodiments of the tube support construction of the invention, described hereafter, is not met, nor the inventive construction suggested by various known support arrangements for horizontal cylindrical members in nonfluidized bed applications, exemplary examples of which are now described.
U.S. Pat. No. 4,356,795, for example, discloses an arrangement in which a vertical support tube is provided with fins welded to opposite sides of the tube. The fins are cut and notched to form generally C-shaped spaces with lower lugs having an upturned lip. A bottom lug engages the lip of the lower lug. The bottom lug has an upper arcuate surface upon which a horizontal tube is seated. An upper lug is also provided which has a lower curved surface that engages the top surface of the horizontal tube. The upper lug, however, is welded to an upper lip of the fin in order to hold the horizontal tube in place. Hence, the arrangement basically embodies the principles of welded supports of the known arrangements described above but, as well, also requires a more complex construction.
U.S. Pat. No. 4,550,690 discloses a steam yoke and hanger arrangement which provides a complex support structure involving U-shaped openings for holding horizontal tubes but which is not particularly suited to support from a vertical tube.
U.S. Pat. No. 2,099,465 discloses a two-piece conductor clamp with a through bolt for securing the clamp to a wooden vertical support and for retaining the two piece clamp in position that supports one or more transversely positioned wires.
In U.S. Pat. No. 1,852,363, pairs of clamping elements are strung or threaded onto vertical tie rods in opposed or inverted relationship relative to one another so that curved arms will embrace a pair of horizontal tubes on opposite sides of the tie rods. The vertical positioning of longitudinally spaced clamps is maintained by sleeves therebetween which circumscribe the tie rods.
Other constructions include a holding device as set forth in U.S. Pat. No. 4,589,618 which discloses a holding device for a tube bundle wherein mating clamp elements grip tubes therebetween under forces developed by bolt and nut arrangements. U.S. Pat. No. 1,824,459 shows a bracket arrangement held on a vertical tube for supporting two transversely positioned tubes. U.S. Pat. No. 3,397,431 discloses a tube clamp assembly wherein through bolts secure mating U-shaped clamp portions having openings to receive tubes. In U.S. Pat. No. 2,893,698 supporting fins are secured to vertical tubes mounted for supporting horizontal tubes which are retained by means of anchoring piece. U.S. Pat. No. 2,981,974 discloses a cable suspension arrangement wherein clamping shoes are held in assembled condition by U-bolt. In U.S. Pat. No. 4,019,468, support means for furnace tubes are disclosed wherein hangers mount U-shaped straps which hold horizontal tubes.